A wide variety of medical implants, in particular intraluminal endoprostheses, are known from the prior art for a wide range of applications. Within the context of the present invention, implants are to be understood to be endovascular prostheses or other endoprostheses, for example stents (vessel stents (vascular stents, including stents for application in the area of the heart and heart valve stents, for example mitral valve stents and pulmonary valve stents) and bile duct stents), endoprostheses for closing patent foramen ovale (PFO), stent grafts for treating aneurisms, endoprostheses for closing an ASD (atrial septal defect) and prostheses in the area of hard and soft tissue. An implant of this type is often inserted by means of a catheter into the organ or vessel to be treated.
Stents and other endovascular endoprostheses have an open-worked hollow cylindrical (tubular) and/or hollow conical main structure, which is open at both longitudinal ends, wherein the main structure is often composed of a multiplicity of crosspieces. In a main structure of this type, for example in the case of a heart valve stent, valvular cusps, for example three valvular cusps, may be arranged on the inner side and form the heart valve and may consist of a plastics or of a biological material, for example porcine pericardium. The stent carries the heart valve and anchors it in the heart.
Catheters are small pipes or tubes of different diameter, which can be introduced into the respective bodily cavity to be treated. During treatment with a catheter, a guide wire and possibly a guide catheter is/are first introduced into the organ or vessel to be treated. The catheter is then advanced along the guide wire as far as the point of the organ or vessel to be treated, so that the implant arranged on the catheter is placed in the region of the point of the organ or vessel to be treated. The implant is then decoupled from the catheter and possibly dilated. The catheter is then removed. The guide wire is also withdrawn from the organ or vessel, either at the same time or subsequently. A catheter that has an inner shaft and an outer shaft is often used to insert a stent.
Stents and other implants normally adopt two states: namely a compressed state with a small diameter and an expanded state with a larger diameter. In the compressed state, the implant can be introduced into the vessel or organ to be treated, through narrow vessels, by means of a catheter and can be positioned at the point to be treated. To this end, the implant is crimped onto the balloon of a catheter for example and is thus transferred into the compressed state. The implant is then dilated at the treatment location, for example by means of the balloon of the catheter, and then adopts the expanded state, in which the implant remains in the vessel or organ and is fixed there, after which the catheter is withdrawn again from the body of the patient being treated. Alternatively, if the main structure of an implant consists of a self-expanding material (for example Nitinol), said implant adopts the compressed state as result of compression below the transition point and adopts the expanded state above the transition point.
A heart valve prosthesis and a deflecting device are known from document U.S. Pat. No. 8,029,564 B2. The system further includes a line, which is passed through the free ends of the stent posts, which carry the heart valve. The stent posts can be bent inwardly by means of this line so as to achieve a closed state. This system, however, is not suitable for non-invasive transfer by means of a catheter to the point to be treated, since it is too bulky in the foot region.
With heart valve stents that can be transported by means of a catheter to the point to be treated, for example the COREVALVE transcatheter heart valve of Medtronic GmbH, complex assembly of the stent is first necessary before the non-invasive intervention so as to assemble said stent on the catheter. Five different tools are currently used for this purpose. The procedure, which is generally carried out by the doctor, is very complex and therefore is highly susceptible to failure.
There is also the problem in the known systems that the sent retention force may be insufficient. This means that the ends of a stent arranged on the catheter may spring out from the fixing in a curve of a vessel through which the system is guided on the way to the bodily cavity to be treated. If this happens, the stent may be placed inaccurately at the location to be treated or it may be necessary to re-crimp or re-capture the stent with the catheter, which is extremely difficult to implement.